As technology development and demand for mobile devices have increased, demand for secondary batteries as an energy source has rapidly increased. Conventionally, nickel-cadmium batteries or hydrogen ion batteries have been used as secondary batteries. However, lithium secondary batteries which are free from charging and discharging due to little memory effect compared with nickel-based secondary batteries have recently widely used, and have a low self-discharge rate and a high energy density.
Such a lithium secondary battery mainly uses a lithium oxide and a carbonaceous material as a positive electrode active material and a negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate each coated with such a positive electrode active material and a negative electrode active material are arranged with a separator therebetween, and an outer material, that is, a battery case, for sealing and storing the electrode assembly together with an electrolyte solution.
The lithium secondary battery includes a positive electrode, a negative electrode, the separator therebetween, and an electrolyte. Depending on which one of the positive electrode active material and the negative electrode active material is used, the lithium secondary battery may be divided into a lithium ion battery (LIB), a polymer lithium ion battery (PLIB), and so on. Generally, electrodes of these lithium secondary batteries are formed by applying the positive electrode active material or the negative electrode active material to a current collector such as a sheet, a mesh, a film, and a foil of aluminum or cupper, and by drying it thereafter.
In addition, although one battery cell can be used alone in the secondary battery, a plurality of battery cells may be used in series and/or in parallel with each other. When the plurality of battery cells are connected in series and/or in parallel, heat is generated, and it is necessary to discharge such heat to the outside.
Conventionally, a thermal interface material (TIM) for transferring heat by contacting the battery cell has been used, but a conventional TIM has a problem in that thermal conductivity is not high.